A conundrum

From Kim Darnell, this puzzle, which she found on Tumblr (no one seems to know the ultimate source, as is usual in such things):

(#1)

You can see this as a puzzle, or you can see it as a wordless cartoon. In either case, it draws on a piece of popular culture, and if you don’t have that, you’re lost.

For Kim, the big point was phonological, but the cultural reference is crucial.

To get over the hump, try reading out the first two items in the sequence, slowly and rhythmically, and let your associative memory listen to what you’re saying:

One fifth. Two fifths.

If this works, you can supply the other two items without even looking at #1 (though the colors of the last two items will now support your guess:

One fifth. Two fifth(s). Red fifth(s). Blue fifth(s).

Calling Dr. Seuss (Thedor Seuss Geisel)!

(#2)

One Fish Two Fish Red Fish Blue Fish is a 1960 children’s book by Dr. Seuss. It is a simple rhyming book for beginning readers, with a freewheeling plot about a boy and a girl named Jay and Kay and the many amazing creatures they have for friends and pets. Interspersed are some rather surreal and unrelated skits, such as a man named Ned whose feet stick out from his bed, and a creature who has a bird in his ear. (Wikipedia link)

The phonological relationship between fish and fifth is in fact very close indeed, since fifth in casual speech is [fIθ], so the difference is just between a palatal and a dental voiceless fricative.

The Dr. Seuss title has given rise to at least one further piece of language play, this time in a Pinterest item (again, with no known source):

(#3)

(Sith and fish differ in their initial consonant — alveolar vs. labiodental — as well as their final, so that they’re more distant than fi(f)th and fish, but still pretty easily relatable.)

Of course, for this bit of play to work, you need to know about another piece of popular culture, namely the Star Wars movies. From Wikipedia:

The Sith is an organization of preternaturally-gifted warriors in the fictional Star Wars universe. It is an ancient interstellar quasi-religious kraterocratic institution with an agenda of galactic domination, led by members who seize power through physical force, social maneuvering or political cunning.